Controlled Assembly and Anomalous Thermal Expansion of Ultrathin Cesium Lead Bromide Nanoplatelets.
basic_science · Level V
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- Record sourced from PubMed, PMID 36884029.
- Also identified by DOI 10.1021/acs.nanolett.2c04526.
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Abstract
Quantum confined lead halide perovskite nanoplatelets are anisotropic materials displaying strongly bound excitons with spectrally pure photoluminescence. We report the controlled assembly of CsPbBr<sub>3</sub> nanoplatelets through varying the evaporation rate of the dispersion solvent. We confirm the assembly of superlattices in the face-down and edge-up configurations by electron microscopy, as well as X-ray scattering and diffraction. Polarization-resolved spectroscopy shows that superlattices in the edge-up configuration display significantly polarized emission compared to face-down counterparts. Variable-temperature X-ray diffraction of both face-down and edge-up superlattices uncovers a uniaxial negative thermal expansion in ultrathin nanoplatelets, which reconciles the anomalous temperature dependence of the emission energy. Additional structural aspects are investigated by multilayer diffraction fitting, revealing a significant decrease in superlattice order with decreasing temperature, with a concomitant expansion of the organic sublattice and increase of lead halide octahedral tilt.